How to read the architectural plans

CarolinaFireJournal - By Jim McClure
By Jim McClure
08/04/2013 -

(Note: This is part three of a multi-issue topic.)

Six months ago I promised we would be talking about how to read building plans, specifically, building plans for firehouses. We are finally there. I will be expanding on the drawing titles from last issue focusing on the architectural pages labeled “A.”

The Floor Plan

All things derive from the floor plan. No one else can add their comments without the pages showing the walls, doors and windows. You all know what floor plans are. You see them on the wall every time you are in a large building staring the red X marked, “You are here”. I assume you may have plans for target hazards in your response area. Those plans have been stripped of all particulars except the walls and doors. Our drawings will need pages of details.


When you are looking at the plan set, North will always be at the top of the page. It may be “nominal north” and not “true north” but regardless of which compass point the front of the building faces, north will always be at the top of the page.

The floor plan pages start with the “A” series drawings. A small, uncomplicated building may only have 20 pages in the “A” series. A large building could have twice that many. Figure A shows a section of a small four-person firehouse and is typical of what you will see when you look at page A2.1 or A2.2. The rest of the building is not shown due to space limitations. There are a lot of lines that will not make sense to you at this point.

Walls, doors and windows

What you are seeing are the walls, doors, windows, room names and/or numbers, furniture, grid lines, dimensions, section cuts, references to interior elevations, and references to those details I mentioned earlier. Since space is limited, a magnifying glass would help from here on out.

The numbers in the circles in the doorways and in the diamonds next to the windows will be found on the door and window schedule page; 11 pages from here on page 7.1. Yes, I know the math doesn’t work here but that is because most of the A pages have subset pages. I won’t necessarily go to the schedule page right now unless I know there is a particular door or window that is out of the ordinary. If door 02 at the right end of the drawing is called out to be wider than normal, I might check the schedule right now. Because most of the triangles have C’s in them, they are of a similar type. The D windows are obviously a totally different style and/or operate differently.

Furniture, Fixture and Equipment

After awhile you will start to recognize the icons for all the furniture. They are standardized across the country. Each bedroom shows, two beds, two nightstands, three lockers and what may be a coat rack. The bathrooms are broken into two sections. One shows the sink, personal lockers and toilet, the other shows the shower and a bench. The crossed lines with the small circle in the middle represent the floor drain. In Room 113, the Utility Room, the dotted lines two different things. The narrow line represents a shelf above the washer and drier. The washer and dryer are dotted because they are not included in the contract and will be provided by others. They are shown so anyone else working on the plans does not decide to but something there. It also tells the mechanical engineer that plumbing is required in that wall.

Dimensions and Grid lines

The dimension lines are obvious but there is some nuance to their use. Look at the four dimension lines starting at the bottom. The bottom shows the entire width of that space. The next three lines up seem arbitrary in what they define. The second, third and fourth line define a combination of windows and walls. Lines from walls are from an edge, either inside or outside. This is about the foundation and structural elements. Dimensions for windows and doors are to the center line of each. When the contractor is going to frame the walls, he will have to look at the window schedule to find the width and height of the window. From our standpoint this makes it harder to verify if the rooms’ internal dimensions and square footage are what you expected. If you have a question about a particular room, you can always ask the architect to verify it for you. As I said in the first article six months ago, usable square footage is precious.

Notice that the horizontal grid lines are marked alphabetically and numbers mark the vertical grid lines. These are reference points for the foundation and all structural elements above. They can be used by anyone using the plans. For example, you could say you wanted an alarm panel on the hallway wall designated by Grid line G where Grid line 7 intersects it. Your chosen location would be crystal clear.

Another example would be telling the architect that the Office is too big. You could say to cut it back from Grid line J to Grid line I. Speaking of Grid line I, it is referencing something on the part of the building not shown in this drawing.

The last three symbols on the drawing refer to Detail Cuts, Building Sections, and Interior elevations. If you look at room 105, labeled FF RR for firefighter rest room, you will see it is surrounded by a dotted line. There is a circle attached to it with a 1 over A1.1 inside the circle. This tells you to look at Detail #1 on page A1.1. There will be a larger drawing of just this space. Additional information you would see is a list of notes explaining all the fixtures in the room plus any other special information you need to know about this space. Paint colors, floor coverings, wall coverings, etc. would not be on A1.1 but on a separate Finishes Schedule page.

There are two symbols linked by a darker line pointing to Room 111 from top down and to room 108 from the bottom up. They terminate in circles with arrowheads pointing to the left. This is called a Section line. It tells you to go to page A-1.7. What you will see there is an interior view of the space. It is as if the building was sliced open at this point from roof to floor and from front to back. You would see everything to the left in the space in front of you. The view stops at the next interior wall. In this particular case there would be side views of the bed and night stand in Room 111. The cut through the Hallway would show the interior door and in Room 108 you would see the bathroom vanity, mirror, toilet, toilet paper holder on the wall and the edge profile of the bench since the Section line goes right through it.

In addition, you will see all the structural elements along this line from foundation to roof. Detail Cuts here will drive to other pages and other drawings. Although it is cumbersome, I usually will follow one path at a time to understand what the architect is telling me on paper. It means a lot of flipping pages back and forth but this is need to know stuff.

The third symbol is a circle with four points surrounding it. This is the Interior Elevations icon. There will be a line attaching the icon to a particular room, in this case, Room 109, the Captain’s bunk room. The icon will have a number over a page number, i.e. 1 over A-1.9. This takes you to page A-1.9, Detail #1. This drawing will show how all four walls look in that particular room.

A word of caution — the Figure A drawing was mocked up just for training purposes. Typically, the floor plan will be page A-2, A-2.1 or A-2.3. That would mean that all the Detail cuts, Section cuts and Interior elevations would be on pages higher in the A-2. Series, not lower as the examples above show. That finished the floor plans for now.

Ceiling plans

As human beings, we only see a ceiling by looking up. Showing what is happening on the ceiling by drawing from the perspective of the floor just would not work. The drawing needed to show what is happening above your head is called the Reflected Ceiling plan.

It is a view of the ceiling from above as if the ceiling and everything attached to it were transparent.

The rectangular lines in the bedrooms and the square lines in the hallway tell us that the ceiling here is T-Bar suspended tiles. I am a big fan of T-bar ceilings if there is plumbing or mechanical equipment between the floors. Popping a tile or two out of the way to fix a plumbing leak is certainly easier than breaking sheetrock. This only works if the tiles are the standard 24” x 48” tiles. A 24” x 24” tile leaves no room for you and the wrench. Architects love the look of the 24” x 24” tiles. You can get the look with a 24” x 48” if you specify the tile with the extra score line across the middle. It looks like a 24” x 24” but is actually a 24” x 48”.

Since the office, bathrooms and utility space have no lines it is assumed that the ceiling is sheetrock. Checking the Finish Schedule will confirm this. The number 09260.B is for sheetrock. Pop quiz — do you remember the name of the organization who supplies the specification number? The answer is in my first article six months ago.

Other items shown here are ceiling mounted light fixtures, wall mounted light fixtures, ceiling mounted alarms and access doors. Each bedroom has three little squares with circle inside. These are recessed can lights. There is a 24” x 48” fluorescent fixture in the middle of the ceiling. There is also a fluorescent light above the locker area. In room 113 you will see the letters “OS” in a small box next to the light fixture. This tells us an occupancy sensor and not a switch operates this light. The Electrical Code requires this is in a lot of rooms.

You will see the label, “15000.A Access Panel” on the plan twice. There is a line ending in a black dot landing in a dotted rectangle. This shows the location of both of those. In room 109 there is a square divided by a diagonal line with a circle in the middle. This represents a HVAC vent.

I will end with two small but important details that you need to know When you are looking at the plan set, North will always be at the top of the page. It may be “nominal north” and not “true north” but regardless of which compass point the front of the building faces, north will always be at the top of the page. Secondly, there is the matter of scale. Architects use architectural scales. Typically, one-quarter inch to the foot is common for drawings depicting the entire building. But that changes for a lot of details pages. Depending on what is being drawn, the scale may be one-half, three-quarters or one inch to the foot.

The Civil pages (these drawings depict all the work either on or under the dirt) always use engineering scales. These call out dimensions as “units to the inch.” In other words, the drawing would be scaled at 10 to the inch, 20 to the inch all the way up to 60 to the inch. Not knowing this could lead to some very messed up plan sets. A worst case example was when the two different teams working on an early Mars probe did not used the same scale. One used standard measurements and the other used metric. The result was the probe crashed instead of having a gentle landing. See you in three months.

Jim McClure is the owner of Firehouse Design and Construction (FD&C). The mission of FD&C is “to help firefighters, architects and government agencies design and build maintainable, durable, and most importantly, functional firehouses.” McClure’s career in public safety spans almost 29 years. For more information visit, or call 408.603.4417.
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